1. Field of the Invention
In the operation and maintenance of coaxial cable R-F transmission systems of the type that are used for cable television (CATV), it is necessary to quickly locate and correct equipment malfunctions or faults. Such systems may have many amplifiers, connector devices, passive couplers, and passive taps, any one of which may become defective during use. An R-F transmission coaxial cable system is therefore inherently prone to service interruptions due to the multiplicity of devices required.
Direct physical inspection of the devices in an R-F transmission system may be very time-consuming, and even somewhat hazardous when equipment is located on poles. Direct inspection requires the physical opening of the system, and the mere act of inspection may cause further interruption of service to customers still unaffected. Still further, if the equipment is not properly reassembled, inspection itself may induce R-F leakage or faults.
It is therefore desirable to have a method and apparatus which will permit the detection of equipment faults or service outage points without direct physical inspection and without climbing poles to inspect each location.
2. Description of the Prior Art
At present the usual method of fault detection is the physical inspection of various points in the system in order to locate faults. If an inspection reveals no fault, then the process must be repeated in a hit or miss fashion until the fault is found. This can be a time-consuming and expensive process which deprives customers of service time and raises service cost.
Often the best indication of service outages and subsequent fault location is the reports of failure received from users of CATV systems. However, this is at best unreliable, and in rural areas is quite imprecise because of the large distance between users. In urban areas, customer reports are also imprecise because of the complex systems and many users.
Several manufacturers presently offer sophisticated and expensive status monitoring and reporting equipment which can identify a failure in any one of hundreds, or even thousands, of in-service amplifiers. These systems merely locate the fault, and it is still necessary for personnel to travel to the site to correct the problem.
In the past, sometimes faults have been detected by common R-F leak detectors while checking the system for leakage. However, this is very unreliable because if a system is without R-F leakage, a person checking for faluts will observe no R-F and consequently be misled into believing that there is a complete absence of R-F in the system. The absence of a reliable, controlled source of detectable R-F emission from R-F coaxial systems renders this approach to the problem almost useless.